thanks bluemele for the info, I will read through it and enlighten myself.

one point for the regression models, little that I learned in my econometric classes, I know that no matter what model you create, the prediction power stays for the next 6 months, correct? So, maybe to this we can attribute the instability of the ranking and the overall general providers performance..what is your opinion?

Well, I think big moves tend to happen dependent upon volatility. I think 6 months is pretty safe, but who knows. Sometimes a big move will happen in May, then another in October, then another in January.

Too hard to predict, and I wouldn't place too much weight on a hard number like 6 months and also they all trade different timeframes so there are micro fundamentals at play.